Data mining enhances scientific knowledge

Short-tailed shearwater. (Photo: Gavin Johnstone)

29th September 2010

Like geological exploration and mining for hidden and valuable assets, data exploration and mining aims to unearth hidden patterns and links within and between sources of scientific data, which add value – in the form of scientific knowledge.

‘Collecting data from Antarctica and the subantarctic is difficult and expensive, so I try to enhance the value of it in a variety of ways,’ Dr Raymond says.

‘This can include analysing multiple data sets to uncover information that would not be apparent from a single data set, or using different analytical techniques to extract new information from data.’

In 2009, for example, Dr Raymond worked with Australian, New Zealand, French and US scientists to study the effects of the physical environment on the foraging behaviour of sooty and short-tailed shearwaters in the Southern Ocean.

Previous tracking research had found that sooty shearwaters made long trips from the south-east and south-west of New Zealand to forage in ‘popular’ areas within the Polar Front – where cold, northward-flowing Antarctic waters meet and mix with the relatively warmer waters of the subantarctic. Short-tailed shearwaters also foraged in the Polar Front, and further south, after long flights from Tasmania and South Australia. The foraging areas of both species overlapped at around 140°E (see figure below).

A: Sooty shearwater tracks (grey lines) and dive locations (black dots), with the short-tailed shearwater habitat utilisation from panel B included for reference. Note the overlapping use of the Polar Front zone around 140°E. The northern and southern branches of the Polar Front (black) and the trawl transect (dotted orange) are shown. B. Short-tailed shearwater tracks from two South Australian islands (red lines) and from Wedge Island, Tasmania (green lines), and their corresponding combined habitat utilisation (background colours). (Graphic PLoS ONE).

By examining this tracking data in the context of ocean bathymetry, sea surface temperature, wind speed, and the abundance and distribution of prey species, a richer picture emerged of why the birds might be foraging there.

‘We used tracking and dive depth data collected during foraging trips by the birds, as well as at-sea observations of the birds over 16 Antarctic shipping seasons,’ Dr Raymond said.

The team found that the birds focussed their foraging efforts in areas where myctophids (lantern fish) and other small prey were more abundant. The majority of the foraging occurred around sunrise and sunset, when myctophids (and other prey that migrate vertically within the water column) would be closest to the surface.

The popular foraging areas corresponded to oceanographic regions where there was a strong upwelling of nutrient-rich water, driven by the interaction of the Antarctic Circumpolar Current with large bathymetric features, such as the south-east Indian Ridge and the Pacific-Antarctic Ridge.

Despite the rich pickings, sooty and Tasmanian short-tailed shearwaters made ‘energetically costly’ flights to their foraging areas. The birds were generally accompanied to their foraging grounds by favourable tail and hind-quarter winds, but battled headwinds on the way home. In contrast, South Australian short-tailed shearwaters travelled to more ‘energetically favourable’ foraging grounds.

However, Dr Raymond said shearwaters use a variety of techniques to reduce energy expenditure in flight, which were not accounted for in the study, such as flying close to the water, where wind speeds are lower, and using wave troughs and wind gradients.

Dr Raymond said the results of the research suggest that shearwaters might be useful as indicators of change in parts of the Southern Ocean ecosystem, particularly the Polar Front zone.

A. Distributions of sooty shearwater dives with respect to time of day (note that most dives occur around sunrise and sunset). Grey bars indicate dives made from 30°S–50°S, and white bars indicate dives made south of 50°S.

B. Dive depths with respect to time of day. The median (cross) and interquartile range (bars) are shown. (Graphic PLoS ONE).